Current analog and digital communications systems, and more specifically cellular radiotelephone systems, define a fixed-rate link between entities or passing traffic information, and include a mechanism to minimize the timing delay between a transcoder (XCDR) and a base-station (BS). Transcoding is a process which transforms a higher rate "chunk" of traffic information into a lower rate (and subsequently smaller bandwidth) of "transcoded", or rate adapted traffic information. In the cellular radiotelephone systems mentioned above, transcoding is done at a fixed rate. Consequently, the number of channels available in a defined link between the XCDR and the BS is likewise fixed.
However, in a code-division multiple access (CDMA) cellular radiotelephone system, a vocoder which generates variable data rates on a frame by frame basis is utilized. The typical link which passes the transcoded information is a T1 Megastream.TM. link, which, assuming a data traffic transfer rate of 16 kbits/s, yields 96 channels. Estimates of future 3-sector cell capacity in CDMA cellular radiotelephone systems reach in excess of 150 channels. Assuming these future estimates are accurate, at least two T1 Megastream lengths would be required to supply future 3-sector cells with data traffic information in a CDMA cellular radiotelephone system. However, T1 Megastream links are installed by system operators, and are leased at a price of approximately $3,000-4,000 per month, per link. If at all possible, reduction of the number of T1 Megastream links required to serve a particular configuration in a cellular radiotelephone system is a formidable goal indeed.
If it is assumed that the variable rate coder described above has an average rate around 4800 bit/s, the result is that speech is present half the time [(4.8 K plus control+framing)/16 k=42% of the given bandwidth is occupied]. Therefore, a need exists for an apparatus and method which makes more efficient use of the variable bandwidth between the variable rate vocoder and XCVR's to minimize T1 Megastream link requirements without physically altering the T1 Megastream link.